ML19347E895
| ML19347E895 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/11/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| TASK-03-03.A, TASK-3-3.A, TASK-RR LSO5-81-05-015, LSO5-81-5-15, NUDOCS 8105140194 | |
| Download: ML19347E895 (4) | |
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n M I 5.'p Docket No. 50-245 MAY I I 1981 g
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Mr. W. G. Counsil, Vice President 1
Nuclear Engineering and Operations
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Northeast Nuclear Energy Company Q/W Post Office Box 270 Hartford, Connecticut 06101
Dear Mr. Counsil:
SUBJECT:
SEP TOPIC III-3.A. EFFECTS OF HIGH WATER LEVEL ON STRUCTURES MILLSTONE 1 Enclosed is a copy of our draft evaluation of Systematic Evaluation Program Topic III-3.A.
You are requested to examine the facts upon which the staff has based its evaluation and respond either by confiming that the facts are correct, or by identifying errors and supplying the corrected information. We encourage you to supply any other material that might affect the staff's evaluation of hese topics or be significant in the integrated assessment of your facility.
four response is requested within 30 days of receipt of this letter.
If no response is received within that time, we will assume that you have no coments or corrections.
In future correspondence regar ing Syst 2natic Evaluation Program topics.
please refer to the topic numbers in your cover letter.
Sincerely, Dennis M. Crutchfield, Chief Operating Reactors Branch No. E Division of Licensing
Enclosure:
As stated M
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See next page
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MAY I 1 1981 Docket No. 50-245 LS05 05-015 Mr. W. G. Counsil, Vice President Nuclear Engineering and Operations Northeast Nuclear Energy Company Post Office Box 270 Hartft.*d, Connecticut 06101
Dear Mr. Counsil:
SUBJECT:
SEP TOPIC III-3.A, EFFECTS OF HIGH WATER LEVEL ON STRUCTURES MILLSTONE 1 Enclosed is a copy of our draft evaluation of Systematic Evaluation Program Topic III-3.A.
You are requested to examine the facts upon which the staff has based its evaluation and respond either by confinning that the facts are correct, or by identifying errors and supplying the corrected information. We encourage you to supply any other material that might affect the staff's evaluation of these topics or be significant in the integrated assessment of your facility.
Your response is requested within 30 days of receipt of this letter.
If no response is received within that time, we will assume that you have no comments or corrections.
In future correspondence regarding Systematic Evaluation Program topics, i
please refer to the topic numbers in your cover letter.
Sincerely,
.y Dennis M. Crutchfield, ief Operating Reactors Branch No. 5 Division of Licensing
Enclosure:
As stated e
cc w/ enclosure:
See next page
MILLSTONE STATION
'SEP TOPIC III-3.A EFFECTS OF HIGH WATER LEVEL ON STRUCTURES I.
Introduction The original design basis high water level including dynamic effects for nuclear power plants is reviewed in SEP Topics II-3. A. B.
Should the design basis level or dynamic effe:ts increase from that assumed in the original design, the abili'v of plant structures to withstand !.his new loading is reviewed. The objective is to provide assurance that high water levels will not jeopardize the structural integrity of Seismic Category I structures and that Seismic Category I systems and components located within these structures will be adequately protected.
II.
Review Criteria Standard Review Plan 3.4 defines analysis procedures for flood loadings and Regulatory Guide 1.102 defines acccptable flood protection.
III. Related Topics and Interfaces 1.
Flood water levels, protection requirements and water induced loads are reviewed in SEP Topics II-3.A, B.
2.
Inservice inspection req'uirements for water control structures are reviewed in SEP Topic III-3.C.
3.
Dam integrity is reviewed in SEP Topic II-4.E.
4.
Classification of structures which need be seismic Category I is reviewed in SEP Topic III-1.
IV.
Review Guidelines A review of the structural design procedures and design loadings for flooding at the site was conducted by searching the docket files and comparing the stated design parameters with current criteria as outlined in the Standard Review Plan and Regulatory Guides.
This review is dependent upon the evaluations of SEP Tcpics II-3. A, B.
Since topic evaluations for II-3.A, B defining current flood levels have not yet been performed, flood levels used in this evaluation were obtained from Regulatory Guide 1.59 and Standard Review Plan 2.4.5.
Therefore, this topic review may have to be modified when the evaluations of Topics II-3. A, B are available.
- o
. V.
Evaluation The design basis water level at Millstone 1 NPS is the probable maximun flood (PMF) level and is stated in the FSAR as being 19.0 feet above mean-sea-level (MSL). All structures are designed to this level except the intake structure which is designed to 32.4 ft. MSL. Tha west wall of the plant building (which is postulated as being most vulnerable) is further protected by a wall to 30.0 ft. MSL.
Regulatory Guide 1.59, Figure C.2 indicates a probable maximum surge of 19.4 ft. MSL.
In the Northeast Nuclear Energy Company submittal dated August 29, 1979, the design water level was stated as being 19.0 ft. MSL.
All structures which do not have reinforced concrete walls are protected by providing a reinforced concrete flood wall to 19.0 ft. MSL. As noted above, the intake structure is designed for a 32.4 ft. MSL loading.
The 32.4 ft MSL elevation accounts for an assumed 13.4 ft. MSL stillwater level and for non-breaking waves above this stillwater level as they strike the structure.
No structural details are described in the FSAR. The dynamic effects of waves were not considered. Combinations of flood loadings with other loadings are given in the Millstone FSAR, Section 12.
VI.
Conclusions Regulatory Guide 1.59 specifies a probable maximum surge (PMS) of 19.4 ft.
MSL with the following limitations: 1) the NRC staff will continue to accept for review detailed PMS analyses that result in less conservative estimates and 2) the PMS estimates are maximum stillwater levels upon which coinci-dent wind-wave effects should be added. As stated, the plant is protected for wave run-up to 19.0 ft. MSL. Standard Review Plan, Section 2.4.5 states that if the applicant's estimates of critical water level are no more than 5% less conservative than the staff's, staff's concurrence will be stated.
The 5% acccunts for differences in judgment on selected parameters, computa-tional inaccuracies, etc. Ninety five percent of 19.4 ft. is less than 19.0 ft. and thus the Millstone 1 plant is considered protected for the hurricane surge stillwater level; however, it is not protected against wind driven waves on top of the stillwater level.
The following items are not resolved by assuming 19.0 ft. MSL as a stillwater level and can only be resolved after Topic II-3.A, B, B.1 assessments have been completed:
- 1) the ability of structures to withstand the effects of waves;
- 2) whether the 19.0 ft. MSL flood wall design has considered both a stillwater height of 19.0 ft. MSL and a lower water level but with dynamic effects of waves, and has been designed for the controlling loads; and j
..:+ 3) the structural consequences of raising the stillwater elevation from 13.4 ft. MSL (as stated in the Millstone 1 FSAR, Section 4.4.2.e) to elevation 19.0 on the intake structure.
In addition to the structures affected by dynamic wave loads noted above, a confirmatory analysis of other structures subject to dynamic flood loading should be performed since no dynamic wave forces were originally considered.
The analysis should consider effects of waves where applicable in combina-tion _ with other loadings, whether or not the design basis flood is changed.
Structures subject to dynamic flood loadings will be determined in Topics II-3.A. II-3.B and related topics.
The Topic II-3. A and II-3.B evaluations should provide the necessary informa-tion to resolve the structural concerns and non-structural problems of wall overtopping and the consequences of higher flood levels on the internal water levels in the intake structure.
This topic evaluation is based on an assumed 19.0 ft. MSL PMS stillwater level and may change depending on the conclusions reached in the Topic II-3. A and II-3.B evaluations.
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